What is the best age spacing between siblings?

Dear Carey,
This is a relatively new question for humans, simply because until babies began using bottles, and a surplus of food for their mothers became available, women's bodies were unlikely to conceive again soon after a birth. In fact, at least 3 years between births seems to be the historical human norm.

Now, however, moms can conceive again quickly, and have the responsibility of choosing what's best for the physical and psychological health of their babies.

An analysis of studies involving more than 11 million women, published in the Journal of the American Medical Association in April 2006, found that the physical health of a baby is much better if his mother waits a minimum of 18 months after the previous baby before she conceives him. Many studies have shown that women are often anemic for a good year after a birth because of the months of iron allotted to the baby and placenta and the blood loss during birth. Babies born to women who get pregnant within the first 18 months after a birth run greater risk for all kinds of delivery-related complications, from anemia to premature birth and low birth weight.

So to give babies the best possible physical start, the current thinking is that they should not be born when their sibling is less than 27 months old. In fact, recent research around the world shows that in countries where nutrients are less plentiful and health risks are greater, kids born before their older sibling is at least three have less chance of survival.

As a psychologist, my focus is on emotional and mental adjustment. The famous Kauai Longitudinal Study found that spacing kids closer than two years apart was a risk factor for both kids, apparently because neither child got enough attention from the mother to create the close mother-child bond that kids need to flourish. However, later data suggested that this is only true when kids live in poverty, which provides a significant additional stressor to the family. A more recent Swedish study supported these results in a very different cohort. In addition, many studies claim that closely spaced second children test as less intelligent.

In a national survey of more than 1,700 teen-age boys, Jeannie Kidwell, a psychologist at the University of Tennessee, found that children had a more negative view of themselves and their parents when their closest siblings were around two years apart. However, if the space between siblings is under one year or over four years, the negativity disappeared. She explained this by pointing out that kids under the age of four are simply not ready yet to share their parents and thus experience intense resentment towards new siblings and lowered self-esteem because they've been “jilted.” Of course, if the children are born within a year of each other, the older child doesn't resent the newcomer because he's not aware of a time before the sibling arrived. That doesn't mean, however, that either child's needs are adequately met when they're within twelve months of age. Dr. Kidwell claims, based on all the combined research to date, that the ideal spacing to protects self-esteem and lessen competitiveness is four or more years.

You asked my opinion as a mother as well as a psychologist.

I loved mothering my firstborn and wanted to be completely available to him for as long as possible. I nursed him until he was three, and we co-slept for a long time. In other parts of the world, a two year old is still considered a baby. It was clear to me from watching other moms that most mothers would be challenged to be fully responsive to two babies at the same time. I'm not saying it can't be done, just that it takes heroic measures and is hard to pull off so everyone thrives. Personally, I have pretty high standards for the kind of parent I aspire to be, and I find that to stay in a good mood I need a good night's sleep and a somewhat calm household. I simply could not imagine being ready for another child until my son was well past his third birthday and more independent.

My daughter was born when my son was four and three months, so he already had his own "outside" life at preschool. He still went into a brief panic, but recovered easily and became a doting big brother. She's now 13, and mentioned recently that he has been the best big brother she's ever seen, always patient and loving and never mean to her in any way. We always felt like a family, despite the age difference of our kids. But it was often a challenge to find a movie that worked for everyone!

Did they play together? Not much. The age difference definitely limited that, but they were also always interested in different things. I still remember him trying to teach her to build a tower and remarking in frustration, “Mom, she's making the blocks into a family!” So I think that whether kids will be playmates depends on temperament, gender and interests as well as spacing. Research shows that kids of the same gender who are closely spaced are more likely to play together, but they are also more likely to be very competitive with each other.

My own brother was only 18 months older than I was born, and had a very hard time when I was born. I was very competitive with him, and he regularly hit me. My younger brother was two years younger, and we never really played together even though we were close in age. My husband's siblings are four and five years older than he is, and he is closer to his sibs as adults than I am to mine, although I love them dearly.

So you can see my bias. Close spacing is a risk factor that we can usually control, unlike most of the risk factors our kids may face. Caring for a baby is an all-consuming experience. If you add work outside the home, in any form, it further dilutes the amount of attention available to spread between the kids.

All that said, I must add that this is a very individual choice. We don't always have control of when these little miracles show up in our lives, and if we're prepared to make our children our top priority, we can almost always be good enough parents to them.

I also believe that having the older child nearby for the birth (thus avoiding a separation during labor), tandem nursing, co-sleeping as a family, and a supportive extended family can all help protect the older child from feeling like he's been displaced when there is close spacing.

I know many fabulous mothers who have spaced their kids much closer together than I have. If a family is up for the challenge and can give each child enough individual attention, I could only be completely supportive of that choice. I would just want to be sure they know what they're getting into!